[cherry-pick] Update build instruction link, remove EoS versions from specifications (#7146)

Update build instruction link, remove EoS versions from specifications (#7137)

This commit updates the README in the build subfolder to point to the
latest version of the build documentation, as the link was updated as
part of previous documentation changes.

It also removes the last two entries from the supported Kubernetes
versions table of the Technical specifications page, as they are now out
of software and technical support.

Author: nginx-bot

build/README.md

@@ -1,3 +1,3 @@
 # NGINX Ingress Controller
 
-This doc is now available at <https://docs.nginx.com/nginx-ingress-controller/installation/building-nginx-ingress-controller/>
+For instructions, read the [Build NGINX Ingress Controller](https://docs.nginx.com/nginx-ingress-controller/installation/build-nginx-ingress-controller/>) documentation.

site/content/technical-specifications.md

@@ -1,10 +1,10 @@
 ---
-docs: DOCS-617
-doctypes:
-- concept
 title: Technical specifications
 toc: true
 weight: 200
+doctype: reference
+product: NIC
+docs: DOCS-617
 ---
 
 This page describes technical specifications for F5 NGINX Ingress Controller, such as its version compatibility with Kubernetes and other NGINX software.
@@ -37,8 +37,6 @@ We test NGINX Ingress Controller on a range of Kubernetes platforms for each rel
 | 3.2.1 | 1.22 - 1.27 | 0.18.1 | 1.5.1 | 1.25.2 / R30 |
 | 3.1.1 | 1.22 - 1.26 | 0.17.1 | 1.4.2 | 1.23.4 / R29 |
 | 3.0.2 | 1.21 - 1.26 | 0.16.2 | 1.3.1 | 1.23.3 / R28 |
-| 2.4.2 | 1.19 - 1.25 | 0.15.2 | 1.2.1 | 1.23.2 / R28 |
-| 2.3.1 | 1.19 - 1.24 | 0.14.1 | 1.1.0 | 1.23.1 / R27 |
 {{% /bootstrap-table %}}
 
 ---